Evaluation of Mitral Flow of Dogs with Chagasic Cardiomyopathy Undergoing the Infusion of Increasingly Dose of Dobutamine
Chagasic cardiomyopathy is characterized by enlargement of the heart, arrhythmias, chronic heart failure and even sudden death. Recent studies have shown that dobutamine stress echocardiography is a feasible and safe test to be performed in dogs, allowing a better identification of cardiac dysfunction. As there is not much available about pharmacologic stress tests in veterinary medicine, this work was conceived to evaluate the mitral flow of dogs with chronic chagasic cardiomyopathy undergoing dobutamine stress test.
For such, two groups were set up: G1 was composed of five adult mongrel female healthy dogs; G2 was composed of five adult mongrel female dogs with chronic Chagas disease, previously determined by indirect immunofluorescent reaction. Dogs undergone echocardiographic evaluation before (1) and during the infusion of dobutamine in increasingly doses: (2) 10 ug/kg/min.; (3) 20 ug/kg/min.; (4) 30 ug/kg/min. and (5) 40 ug/kg/min. It was measured the peak velocity flow of E (PVOE) and A (PVOA) waves. Afterwards, it was calculated the relation between such variables (PVOE/PVOA).
For G1, PVOE (m/s) started at 0.55±0.11 before the infusion of dobutamine and reached 0.89±0.06 at the highest dose. For G2, it varied from 0.50±0.08 to 0.73±0.14. For PVOA (m/s), G1 started at 0.55± 0.09 and reached 0.75±0.04 at the highest dose of dobutamine, while G2 started at 0.53±0.08 and reached 0.81±0.20. For G1, the relation between both variables started at 1.01±0.12 and reached 1.20±0.10, while for G2, it started at 0.98±0.34 and reached 0.91±0.13. Such data were submitted to a variance analysis, which determined a significant augmentation in PVOE of G1 (P=0.0003) and G2 (P=0.0102) during the increase of dobutamine doses. It was also seen a mild increase in PVOA of G1 (P=0.0001) during the test. The relation between PVOE and PVOA showed no significant variation during the infusion of dobutamine in comparison with basal values. By the other hand, when Tukey´s test was applied to compare between groups, it was verified that G1 and G2 differed in all moments but the basal. It was also observed that the relation of PVOE and PVOA of G2 were always lower than the value one, in opposition to G1.
Results allowed concluding that dogs with chronic chagasic cardiomyopathy have an abnormal ventricular relaxation, characterizing an important diastolic dysfunction, which was better determined when dobutamine was infused.